Developing the Deltawing

One of the most significant racecars ever, will be on show to the public for the forst time in England at Birmingham’s NEC during Autosport International on 10-13 January 2013. It stunned the crowds at the 2010 Chicago Auto Show, and it shocked the racing establishment.

Originally designed as a 2012 Indycar concept the Deltawing was certainly different, but then so is the man who dreamed it up, Ben Bowlby. The English designer was dubbed ‘the next Colin Champman’ by a British television documentary before he had even started to work full time in Motorsport. His last major project was the development of the Laurel Hill Aerodynamic Test Facility which literally turned wind tunnel testing inside out. His new car was striking to look at with a very narrow track at the front with a conventional width rear end. But there were no wings to be seen at all – indeed all of the downforce would be generated by the cars floor.
“We wanted to make a car that is twice as efficient in every way, it should use half the fuel, cost half as much, use half the engine power and weigh half as much yet still go as fast or even faster than a current Indycar” explained Bowlby at the cars launch.

But despite people like Peter Wight describing the car as “a work of genius” it proved to be far too radical for the seemingly conservative ICONIC group who would decide on which design to use for the 2012 Indycar season (they played it safe and plumped for a Dallara instead). When Indycar rejected Deltawing concept many thought that it would be the last time anyone would see the radical design. However the English designer was not keen to give up on the idea and continued to develop it.

There were thoughts of making a spec series based on the cars or possibly a new ‘open source’ racing formula with engineering freedom using the Deltawing as a base model. But Bowlby’s real target was hinted at in early 2011 when he sent Racecar Engineering the image below to illustrate an article
The closed cockpit and lights on the car could mean only one thing, a sportscar (or that Bowlby had replaced Lucius Fox as the head of Wayne Enterprises Applied Sciences). But it did not fit into any classification plus it was only a single seater. But at the Le Mans 24 Hours in 2011 Bowlby appeared and it was announced that the DeltaWing would run as the 56th entry in the 2012 Le Mans 24 Hours, a slot reserved for innovative technology.
The new look Deltawing was not in the end a coupe, but an open two seater with the mandatory twin roll over structures found all open Le Mans cars. Further revisions included a smaller more faired in sidepod replacing the previous design which looked more like something borrowed off a Grumman A6-Intruder.
But getting an entry to Le Mans meant that the team actually had to build the car, and that meant that it would need a homologated chassis. Building one from scratch is fearsomely expensive so Bowlby decided to use an existing design. It just so happened that the disastrous Aston Martin AMR-ONE LMP1 project had just been abandoned and there were a number of abandoned tubs sat around at Prodrives HQ. It was perfect for the Deltawing. Whilst using the wider LMP tub would expand the middle of the car it would not drastically change the concept and it would reduce the crash test requirements. “The two-seater LMP1 tub is almost a drop-in fit to the DeltaWing concept. The 30 inch-wide front body work width is close to that of a two-seat sportscar FIA cockpit” Bowlby explained. The transmission and front suspension were the only other major areas where special development was required from a chassis point of view.

The EMCO built transmission weighs just 33kg and only has five speeds compared to the more conventional 6 speed transmissions used in other LMP cars. “The torque curve that we’re anticipating is very flat and we will take the weight advantage and reduce complexity. Running a five-speed and reverse keeps the gearbox light and small. We did spend a lot of time on the gearbox, which is one of the key elements.”
Within the transmission, a torque-vectoring differential will be employed to maximize tire life and to fine-tune the DeltaWing’s balance.
“First of all, the car does not need torque vectoring to make the car handle, or to get around a corner,” Bowlby clarified. “Our system is to improve handling through a system we call ‘efficient torque vectoring.’ We don’t use braking force with our system. We use planetary gears on either side of the differential. The external ring gears of the planetary sets are connected by a cross shaft and drop gear, such that we can turn the external ring gears of the planetary gears with an electric motor so create a differential of speed between the rear wheels, to a degree of our choosing, without altering the average speed of the pair. The differential speed (torque effect) will be controlled by a simple algorithm that will look at steering angle, lateral acceleration, and the path of the car.”
The wheels and front suspension were a major challenge, for starters nobody makes wheels that are only four inches wide with a three stud pattern, well unless you want to use wheels from a Citroen 2CV, which would, we are informed by a grinning Bowlby, bolt right on (we are not sure if we believe him).
As is the case with the wheels nobody makes a racing tyre to suit this rim size either, well that was the case until Michelin got involved with the project. The final DeltaWing front tyres are just 10/58-15, or less than 23 inches (58 cm) tall, and with a tread just four inches (10 cm) wide. By contrast, the 2011 Le Mans-winning Audi R18 TDI turbo-charged-diesel prototype utilized taller and wider front 36/71-18 tyres, approximately 28 inches (71 cm) tall with nearly 14 inches (36 cm) of tread width.
The rears are less dramatic in size, because the DeltaWing is designed to race with 31/62-15 tyres while the average LMP2 rear tyre is sized at 37/71-18.
Inside the tiny front wheels and tyres are specially developed brakes from PFC in the USA. The DeltaWing’s brake package was a collaborative effort between Performance Friction engineers and the Deltawing team with a very specific set of design criteria. The brake package includes Performance Friction’s Patented Continuous Fiber Carbon-Carbon Disc and pads along with forged aluminum monoblock ZR43 and ZR41 Zero Drag Calipers with patented pad retraction system. The ZR43 is popular with NASCAR teams running on super speedways like Daytona.
“The front of the DeltaWing is extremely compact so we had to be very creative with the packaging of the design to ensure adequate performance over 24 hours, while keeping the component weights to a minimum. The car is unique in that 60 percent of the braking occurs at the rear wheels, but that doesn’t mean we could ignore the front” explains Bowlby.

Aerodynamic development of the car was largely carried out at the Wind Shear full-scale tunnel in North Carolina, and in CFD. Unusually for Bowlby his own Laurel Hill facility was not used.
The lightweight rapid design philosophy lead Bowlby directly to another leading engineering firms door, CRP technology. The unique design and construction of the Deltawing relies heavily on a cleaner aerodynamic shape that achieves a low drag coefficient while still creating enough downforce to turn competitive laptimes. This improvement requires less power to push the air at higher speeds, and improves the efficiency of the vehicle operation.Air filter used only on development car

Aerodynamic advantage was not the only goal of the DeltaWing team. Accelerating the car from low speed corners with only half the available power means the car can only weigh half as much, so an extreme weight loss program was key making the car work.

To compound the challenge, the timing was a very short 7 months from design to the first track test. So the team decided to use 3d printing technology together with the Windform high performance materials where applicable to shortcut the manufacturing time and save every bit of weight they could.
During this process, Laser Sintered Windform XT 2.0 was used not only in prototyping and testing, but in mission critical applications on the car during the 24 hours of lemans race, and continue to race at the Petit Le Mans, in the US. The DeltaWing team was able to move the bar for both racing and Additive Manufacturing applications forward.

The carbon fibre reinforced Windform XT 2.0 was used to construct the gearbox side covers: The DeltaWing utilized a non- “stressed member” engine and gearbox to reduce the structural requirements of the assembly as well as reducing the vibration loads introduced into the lightweight car.
The gearbox with integral bellhousing came in at a svelte 33kg, a fraction of the transmissions it shares the track with. Zack Eakin was the DeltaWing engineer responsible for the design of the gearbox and had this to say about the role Windform played in the design:
“Once we realized that we could use Windform XT as a race-able part at the elevated temperatures & pressures we run the gearbox oil at, it opened up a big possibility for us that would have been cost & time prohibitive otherwise. We went for a design that put the output seal on the halfshaft rather than around the outside of the Tripod joint which represents a big reduction in parasitic losses. But this design means that you have a seal that moves with suspension travel, a non-rotating CV Boot that will react the seal drag, and that you need to somehow get oil into the tripod cavity. Creating a metallic part that would orient the CV boot perpendicular to the average halfshaft angle, with integral oil drillings was a 5-Axis machining job that still would be heavier than what Windform gave us. With rapid prototyping technology we were able to make a very complicated geometry, keep gentle radius’s in the oil passages, and get rid of all unnecessary material without introducing great cost or lead time in the parts. We were able to bond the CV boots directly to the Windform, seal directly to them with an O-Ring, and run the part at temperatures as high as 135oC, and pressures over 1 bar gauge without any issues. Windform was a real homerun for us on these parts”

Zack also believes the electrical enclosures were another very good fit for RP technology “We designed a number of our own electrical controllers for things like the DRS & differential that we needed enclosures for. All an electrical enclosure needs to be is waterproof, durable, and have sufficient heat dissipation for the circuit it houses. We found that we couldn’t make an aluminum housing that was as light as a Windform one, let alone cost or time competitive. Often we would make a simple aluminum lid that the PCB would mount & heat sink to, which screwed into a windform box via some tiny threaded inserts.”
Windform XT 2.0 was the material mostly used for the manufacturing of parts as it represents the top level material for its mechanical & thermal characteristics. The use of 3d printing and Windform materials were fundamental to shorten the timing of car construction. In this case CRP Technology and CRP USA worked to support step by step the technical staff of the Delta Wing team in order to help them finding the best solution.

The first test
It turns! A few shakedown laps were conducted at Buttonwillow raceway, to prove the cars concept – it worked. But it was far from complete! A later test at Sebring also went well.
At Buttonwillow a generic RML 1.6 litre global race engine, note the aluminium cam cover visible above, but a bespoke engine would need to be constructed for the car.
Funding for the project and especially the engine came from a very unexpected source, Nissan. Darren Cox, now the firms motorsport boss, pushed for the company to back the project and supply a new engine via its long time collaborators RML.

The new engine was an incredibly lightweight (far lighter than any FIA-specification GRE unit) turbocharged inline 4 with direct injection. It ticked all the boxes and ran faultlessly out of the box. The car was ready for Le Mans.

At Le MansQuite correctly much curiosity surrounded the Deltawing since it was first announced. One of the questions they all asked was “will it steer?” the answer is yes, but how well will it steer was another question, with the car very capable in a straight line clocking up 306.9kph on the straight without having the correct gearing, pretty much as fast as any LMP2.
In the corners though it was the 29th fastest through the Porsche curves, and 45th fastest through the Ford chicane section. But that is not to say that the car cannot corner, the team were not trying for very fast laps when RCE did its timing, and the ACO had made it very clear to Bowlby that they did not want the car to lap faster than 3m45.
The team was forced to use wing mirrors on the car, though it had originally planned to use a Corvette style camera only. Using the mirrors adds 8% more drag according to Bowlby.
Despite the huge differences between the Deltawing and its base car the Aston Martin AMR-ONE, some things are retained such as the steering wheel and the driver control panel.

AFTER LE MANS
Le Mans did not end well for the DeltaWing team, but they would be back for more at Petit Le Mans, but it did not start well.

The accident in France was caused by a driver not being able to see the tiny black machine, and its profile compared to other cars is very obvious in the image above. To make the car more visible its roll hoops were painted a bright colour, but it did not work for everyone. Eventually the car was rebuilt and finished the 10 hour race North of Atlanta. That was going to be the end of the DeltaWing story, until the American Le Mans Series announced that the car could run the full season in 2013, and then NASCAR announced that in 2014 the car could continue as a LMP2 in the new unified North American Sportscar Championship, it will now be competing with Daytona Prototypes for the outright win at the 2014 Rolex 24, and it will later that year finally get to run at the track it was first designed for – Indianapolis.

Among the American exhibitors at the event, Aurora Bearing Company will showcase the DeltaWing project at Stand 8330 in Hall 8 during the 10-13 January 2013 event, having supplied rod end and spherical bearings for the project.

“Our involvement with DeltaWing has been incredibly rewarding, it’s been an honour to be part of such a significant race car project,” said John McCrory from Aurora Bearings. “Everywhere the car has gone, it’s turned heads, and we’re looking forward to showcasing the concept to fans at Autosport International.”

“DeltaWing is a perfect example of motorsport innovation, challenging the status quo and offering an alternative,” said Ian France, Autosport International Show Director. “It’s less than a year since it first appeared in public, and it’s really struck a chord with the motorsport community. We’re excited it will be a part of Autosport International 2013.”

DeltaWing will join a range of exciting new motorsport machinery at Birmingham’s NEC during Europe’s largest dedicated trade show. British manufacturer Radical will launch its newest supercar, the RXC at the show, along with the Sin 01 race car project.

Sam Collins has worked for Racecar Engineering for more than a decade. His passion for racing began during his work experience in the loom shop of Williams F1 aged 16 and he has been involved in the sport ever since. Sam attended Oxford Brookes University to study Automotive Engineering and has written for many publications since, including Motorsport News and Autosport. He is Associate Editor of Racecar Engineering

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